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genital 5mm' @anni tffiterii YON `INILLIAM P. UHLINGER AND JUSTUSDOERING, OF PHILADELPHIA,

IMPRQVEMENT IN CNSTRUCTING sLATn-r-Rmvms The Schedule referred, to intliese Letters Patent and making part f the um..

To all whom it ma/y concern:

Be it known that we, WILLIAM P. UHLINGER and J Us'rUs Dominic, both ofthe city of Philadelphia, and State of Pennsylvania, have invented a newand useful Improvement in Slate-Frames; and we do hereby declare thefollowing to be a full and exact description ofthe same, reference beinghad to the accompanying drawing, and to the iigures and letters ofreference marked thereon;

The object of our invei'ition is to produce school or countinghouseslates, of a very strong and perfect construction, at a lowmanufacturing-cost, and to form the ljoints of their frames in such amanner that they cannot be tampered with, or picked apart.

The slabs of slate furnished in commerce are not of l strictly uniformdimensions, although nominally of a given size, by which they aredistinguished in trade, and therefore a very important practical featureof our improvement consists in the facilities it provides for adjustingthe size of each frame to the exact width of its particular slab ofslate, so that the latter is not only prevented from shaking within theframe, but

actually strengthens and preserves the frame very materiaily.

In order that our invention may be fully understood, we will now proceedmore particularly to describe the same. l

On reference to the drawing making part of this specification, and inwhich similar letters of reference allude to like parts throughoutthe-several views- Figure 1 is a plan of our improved slate, with one ofthe long bars of the frameA detached;`

Figure 2 is a side View; and

Figure 3, a sectional end view.

The .frame consists of two longitudinal bars, a c, and transverse bars,b b.

All 'have their inner edges bevelled, as seen in the drawing, and areprovided with a groove, 0,' to receive the slate A.

The long bars, a a, are made to correspond in length, as nearly aspracticable, with the length ofthe slate A.

They are, at both ends, provided with short tenons, l

are glued, so as to give due strength to the frame, for the additionalhandling required for its completion, as follows:

After the glued joints are set and hardened, a hole is ,drilled at eachof the four joints, passing transversely through the end lbars b b, andentering the long bars a a en dwise, in the manner fully shown in thedrawing. Into these holes is then tightly fitted and glued a series ofstrong dowel-pins, e e, and, lastly', the outer edges ofthe frame aredressed. and the corners rounded, as seen in the drawing.

It will be readily evident that the dowel-pins e e, when once in theirplaces, as described, cannot be withdrawn or tampered with, as is thecase when they pass transversely through the mortse-joint, and areexposed at both lends.

Having thus described the nature of our invention,

What we claim as our improvement, and desire to secure by LettersPatent, is-

A joint for slate-frames, constructed as herein described, having tenonsd litted in grooves c, and iirmly united by dowel-pins e, in the mannerand for the purposes specified.

WILLIAM P. UHLINGER. JUSTUS DOERING.

Witnesses:

GnRIsTIAN PFLAUM, WM. Nuna.. I

